Every time I read about the Anthropic principle I get the feeling I'm missing something. Enthusiasts of the principle seem to be committing a fallacy; perhaps someone can explain why they're not, or why they are. I compare the principle to this. A group of friends get together and decide they'll roll a d20 to decide how to spend the evening. There are various options afoot, but they decide that only if they roll a 20 will they play board games that night. Lo and behold, they roll a 20 and spend the evening playing board games. Later someone says, "How lucky we are to be playing board games!" A skeptic says, "Whatever do you mean by 'lucky'?" Reply: "Well, there was a 1 in 20 chance, and we hit it! That's pretty lucky." The Anthropicist snorts and says, "Hardly! We're not lucky at all. There was a 100% chance. After all, we're playing them." Is that a good analogy? Or does it miss something crucial on one side of the argument or the other?
Here's a better analogy. Joe has OCD. Every morning, he rolls a d100, and if it comes up 1, he hosts a board-game party that night.
On day XX/YY/ZZZZ, Joe hosts a board-game party and a bunch of people show up. During the course of the party, Joe reveals to everyone his d100 policy.
Tim asks him what his die-roll this morning was. Joe tells Tim that he rolled a 1. Tim exclaims "The only reason we're here is because you rolled a 1! How did this incredible piece of luck come to pass?"
Adam responds "There's nothing incredible about what happened. If Joe hadn't rolled a 1 today, we wouldn't be here. We would never have this discussion, or have it on some other day when he does roll a 1."
"Does Joe do anything at all if he rolls almost anything other than a 1, or does he just lie in bed? If the very large die is only rolled once, and all non-1s are very boring, then it is remarkable that we're here."
That's a very interesting point you raised, and I was thinking about this as well. If the universe only "exists once", and life is very unlikely but it still came to be, then it does seem remarkable.
However, this is based on the presumption that life is non-boring, and all other potential universes devoid of life are boring. This seems like a very subjective presumption. Clearly we are biased towards thinking that our own existence, or the similar existence of "life" is special. But a skeptic would claim that from a purely scientific perspective, there's no reason to believe that a universe without life is any more boring than our universe.
Well, but there is something fundamentally and essentially special about conscious minds. A universe that is complete unperceived is, first of all, harder to even imagine than it first appears and, second, would be neither boring nor interesting, since both of those words, and all other assessments, only have meaning within the context of conscious perception. So I would affirm the presumption that "life", in the sense of the existence of conscious minds, is non-boring and universes devoid of life are either boring, or inconceivable.
Ah, thanks. That's helpful. So would you say that the appeal of the Anthropic principle depends on the multiverse theory (or something similar): the idea that there are an infinite number—or a great many, anyway—of "die rolls", an infinite number of attempts?
Yes, though there is an important difference between the multiverse approach and the multi-star/multi-year approach. When we imagine the state of affairs in which many universes are created with random parameters, we tend to give those many universes great variety, and we require each one of them (in our imaginations) to be "fruitful" at least in producing a universe. But it's not clear that the mere presence of lots of years (as many as you like) or stars (as many as you like) are fruitful in the same way. To put it back in terms of Joe the die roller, it's as if Joe wakes up most mornings and just lies in bed all day, not rolling the die. Occasionally—one day in a billion—he rolls the die, and it's a trillion-sided die, say. But I suppose the point is the same: the Anthropic principle says that however unlikely conscious minds are, if they do appear (at whatever odds), then... well I'm not sure where to go from there. Then these minds will ask questions about their existence? But that doesn't seem a very remarkable insight.
The anthropic principle goes the other way. It says that if the questions about existence are being asked, then we don't need further explanation of the lucky die roll.
A less silly line of reasoning is trying to explain why the constants in physics have the values they do which permit life as opposed to the bulk of values that don't. One explanation for this is all possible universes exist so naturally we find ourselves in one compatible with us which is a kind of anthropic reasoning. Other possible explanations being they result from something we don't understand, or that God did it.
I get a sense that the idea behind the anthropic principle is that the subjective experience is antecedent to objective reality, perhaps similar to solipsism or panpsychism.
More like the universe rolls a die, and if it comes up d20^1000, it creates a group of friends playing board games. There's no possible way for the friends to be unlucky, because in the unlucky case they simply don't exist.
In your case, in 19/20 possible worlds, there will be a group of disappointed friends not playing board games. It is reasonable to look for an explanation of why one finds oneself in the 1/20 case and not in the 19/20 case.
In the anthropic principle, in (N-1) cases there is nobody there to ask the question. Therefore, given that there is an entity capable of asking the question, there is no need to explain why that entity happens to find itself in a universe where question-asking entities are possible. Given that the friends exist at all, there is no need to explain why they are playing cards.
The anthropic principle doesn't answer the question of why there is a universe at all, how many universes there are, have been, or will be, or how many universes have contained intelligence. All it says is that we should not be surprised to find ourselves in a universe where intelligent life is possible, since it would be impossible for us to find ourselves anywhere else.
A Boltzmann Brain is (very roughly) a "brain", i.e. self-aware entity, that appears spontaneously in the middle of the universe due to random quantum fluctuations. In an infinitely old and infinitely large universe this should actually be a common occurrence. So why are we not Boltzmann Brains ourselves? Why are we all here observing the universe clustered together on this one planet a mere 15 billion years since it came into being? Why is there so much structure?
I believe the concept is a little different than what you stated. It starts with the assumption that the Universe is actually in or very close to a maximal entropy state, which is orders and orders of magnitudes more likely than the low entropy state we perceive. The idea of a Boltzmann brain is that a downward fluctuation in entropy from this maximum entropy state could result in forming a consciousness with our associated memories and experiences and this is more likely, statistically speaking, than the alternative possibility: that we actually live in an extremely low entropy state of the Universe.
> "In an infinitely old and infinitely large universe this should actually be a common occurrence. So why are we not Boltzmann Brains ourselves?"
Because our Universe is neither infinitely old (is about ~14 thousand millions years old) nor infinitely large (is about 90 thousand millions ly in diameter).
Now this might seem big for you, but it's actually infinitesimal when compared to the number of necessary permutations in order for higher intelligence to appear solely by a quantum fluctuation.
This means that the only scientific possibility for higher intelligence to appear, is then that only a very small set of universe conditions must occur so that atoms then stars then planets then life then intelligent life has the time and conditions to form.
This is the diameter of the observable universe. We don't know if the universe is infinitely big, but all signs (e.g. the flatness of space as far as we can measure it) point to it being infinite, or very very much larger than our observable sphere.
I don't understand why I'm constantly having to inform smart people of this very basic fact. Is there something wrong with the way we teach astronomy? Can you help me spread the word?
Could you expand on the "all signs" bit please? I was under the impression that there was little to no evidence of anything much outside the observable universe.
Read about measurements of the flatness of space. To the precision we're capable of measuring, it appears completely flat.
Then picture us as ants on a surface that appears flat as far as we can see. Are we on an infinitely sized surface? Either we are, or it's a sphere but the surface is curved but so slightly that it appears flat. This implies the sphere is much bigger than our observable area.
Note, we're assuming the universe doesn't just end we arbitrary boundaries. It either is infinite or it curves back on itself.
> ""90 thousand millions ly in diameter"
This is the diameter of the observable universe. We don't know if the universe is infinitely big, but all signs (e.g. the flatness of space as far as we can measure it) point to it being infinite, or very very much larger than our observable sphere."
Our observable sphere is nowhere near 90 thousand million ly in diameter since that would violate relativity. Our observable sphere in ly is always smaller than the age of the universe in years (so ~14 thousand million years).
Also, what you said is no fact, basic or not, it's just some misconception you have about cosmology so you should stop spreading that word since you are misinforming people you talk to.
In a nutshell: A Universe that begins in a singularity cannot have an infinite diameter and while it's true that we do calculate the size of the Universe by assuming the expansion rate right after the Big Bang and that rate might be wrong, it still cannot be infinite without violating the major principles of physics and the all big bang theory.
My "fact" doesn't refer to the universe being flat. I would never call this a fact. The "fact" I referred to is that the universe appears to us to be flat as far as we can tell.
Our observable sphere in ly is always smaller than the age of the universe in years (so ~14 thousand million years)
This ignores the basic fact that the universe is expanding at an accelerating rate. I'm comfortable calling this one a fact. Many 9s behind that confidence percentage (even if the number of nines was recently lowered).
A Universe that begins in a singularity cannot have an infinite diameter
Based on what logic? You are probably imagining an infinitesimally small sphere expanding out and becoming the universe. This is a good description of only our observable universe. There's no reason not to think that point wasn't part of an infinitely large manifold. This would point to an infinitely large universe.
I'm not an expert, but in my curiosity I've spoken to Dr. Don Lincoln from Fermilab about this very topic, so that's the source of my confidence. Along with my own subsequent (armchair) research. I've since followed up and done my best to understand why this misconception is so prevalent. I'm convinced it's because many sources say "universe" when they mean "observable universe", leading to many misconceptions.
> "This ignores the basic fact that the universe is expanding at an accelerating rate."
And that ignores the basic fact that information about those parts of the Universe didn't have time to arrive yet (that is where relativity is violated). You are mixing the concept of "observable universe" with "observed universe". At a given time, given the expansion rate of the universe you have an "observable universe" (those ~90E9 ly), but it will only be fully observable somewhere in the future, in the present you only get to observe ~14E9 ly). In a nutshell what you are proposing is that we are observing particles with infinite redshift. Or perhaps in a simpler way: You can be observing today parts of the universe that are (for instance) 25E9 ly away today, but you are observing particles of light that left that part of the universe a long time ago so that the c x t condition was never violated.
> "This is a good description of only our observable universe. There's no reason not to think that point wasn't part of an infinitely large manifold. This would point to an infinitely large universe."
Based on the theory of the Big Bang which is the de facto theory accepted by Cosmology. It is true that you could have an infinitely large manifold and that is a very interesting theory. But I was answering inside the actual theory that is the accepted one now-a-days the Big Bang (and I actually referred that in the answer). Also, even inside the manifold theory theory, our universe that is what is being discussed here, would still not have an infinite diameter.
There is a difference between the size of the observable Universe now and the size when the light was emitted. It does not violate relativity to state that objects that were 14 billion light years away when the light we see from them left are now much farther away due to expansion.
Furthermore, your reference to relativity is also incorrect. The expansion of the Universe is not caused by objects moving away from each other, which would be limited by the speed of light. The expansion of the Universe is actually an expansion of space itself, which is not limited by the speed of light. You should look up the "metric expansion of the universe".
In general, relativity is known to be incomplete on a cosmological scale. The situation is much more complicated due to the existence of dark energy and dark matter. You should read about the Lambda-CDM model if you want to learn more about the state of modern cosmology.
I didn't quote you or claim you said anything. I made some assumptions about why you made certain statements like the fact that you think the Universe being ~90 billion light years in diameter violates relativity (it doesn't and this is the currently accepted estimate for its size).
You could just clarify your statements/reasoning to try and progress the discussion instead of getting overly defensive.
> "you made certain statements like the fact that you think the Universe being ~90 billion light years in diameter violates relativity"
I was the one explaining to the OP of the thread that the universe is 90E9 ly in diameter (and also, just to clarify for the future so that it doesn't get mixed up yet again, that this is just an approach based on what we know about the history of the universe), it is therefore ridiculous that I also said that it violates relativity. So, sorry if I'm "overly defensive" about you mixing everything up and me having to use my time to answer you so that you don't twist everything I said on the thread.
You made the original claim that it violates relativity so why don't you take your own advice and be more explicit.
The current accepted size of the observable universe is ~90 billion light years in diameter. If you were referring to some other statement that you think violates relativity then feel free to clear things up.
if you're upset about people making assumptions about your comments then (calmly) address those and clarify your point(s). Don't make aggressive and pejorative assumptions of your own.
If you don't know what I was referring to, then why where you so sure that "it doesn't violate relativity" then?
The statement was made about the infinite size of the Universe and the OP (along the way) was talking about the observable Universe. He is mixing the extent of the Universe with the spatial dimensions of the Universe (so, the better word here is actually space). It is still an open debate if the dimensions of the Universe (space) are infinite (although what we knows seems to point that way), but the extent of the Universe is not infinite, if it was, that would violate relativity (or the standard model as I explained along the thread).
Because our Universe is neither infinitely old (is about ~14 thousand millions years old) nor infinitely large (is about 90 thousand millions ly in diameter)
You have just suggested the universe expands at roughly 6c, no?
In the early moments after the big bang, the metric of the universe expanded much faster than the speed of light increasing it's size way above the c x t linearity.
This doesn't violate relativity though, since what is expanding is the length of the spacial dimensions, but the particles between themselves are moving slower than the speed of light (imagine 2 points in the surface of a balloon when the ballon is inflating).
The acceleration of the Universe has not been constant. In the very early Universe there was a period called Inflation where the speed of expansion was much much much faster than the speed of light.
Is there any way to tell that you are not, in fact, a Boltzmann brain with simulated memories and inputs that just imagines everything else exists? I assume it's hard to refute, like Solipsism?
> In an infinitely old and infinitely large universe this should actually be a common occurrence. So why are we not Boltzmann Brains ourselves?
Our Universe of 13.8 Billion years (think: just 13.8 G years -- my fingernail-sized camera card has more bytes than that number) is infinitely younger than an infinitely old Universe.
I didn't word my post very well (I posted the "infinitely old" comment), but what I meant was that it should be more likely to be a Boltzmann Brain in an infinitely old universe than a human standing on Earth in a ~14 Billion year old universe. So why are we the latter rather than the former? That's basically what the anthropic principle is all about. The fact that we are the latter tells us a lot about how the universe, or universes as the case may be, work.
We can't forget that Boltzmann was purely thinking of (near) equilibrium structures. Structure emerges spontaneously minimizing free-energy, totally OK with LBs high entropy laws.
Something vaguely related I've been thinking about: When looking at the timeline of life (link below), humans are a completely negligable slice of history. Dinosaurs survived for about 170M years, modern humans have existed for just 200K, civilization for about 10K, and the technological boom has been here for roughly 100 years.
Can this be seen as evidence that the timeline of humanity will be relatively short in the big picture? Because it would seem like a strange coincidence to be born at the beginning of it. This is even more true for the survival time of humans with modern technology. Assuming the era of technologically advanced humans will last for, say 200M years, it's extremely unlikely to be born at the first 100 years (0.00005 %).
It's interesting to think about how civilization would develop over hundreds, thousands or thousands of thousands years. There have been some pretty significant changes in just the last 100 years, what could happen in millions of years? Civilisation is not a stable system, it seems to be quite volatile. And unlike before, changes and disruptions are not as locally constrained. Perhaps after many thousands of years, there will come a low-probability event that civilization won't recover from.
Imagine you are a soul, in limbo, somewhere outside the universe and elsewhere in another part of reality the universe is progressing through its motions as time goes on. You are an other-reality-style being, yet somehow still allocated as "going to be a homosapiens on Milky Way\Sol\Earth", and your birth will be random during the era of homo sapiens.
Now you can argue about the likliehood of where this random birth happens.
On the other hand, take away the other place, and the souls, and the spooky assignment of types, and just look at the universe as a thing of matter and energy. Some configuration of matter was born to your parents, from their DNA. It is intimately connected to its surroundings by a continual stream of light, heat, air pressure, physical pressure; over millions of seconds it learns. It learns the patterns of air pressure that correspond to other people talking to it, and it learns what things it can and can't push by trying, and what other people talk about.
And it says "isn't it unlikely that I was born here and now, instead of some other time?"
And the question makes no sense. _What_ could have been born somewhere else? or somewhen else? Without its parents DNA, without its particular twenty continuous years of sensory input that it learned from, it would not be itself.
Some other matter, born to other parents, with other DNA, and other childhood experiences, and other knowledge patterns. It would be someone else. Entirely someone else. And ... that happens, we call it "other people".
If you don't believe in a soul, or something like it, what does it mean for you to possibly "be born somewhen else"?
The question is, what is the probability that a person picked at random from the human population, would be born during a technological era. We can work this out. Then, what is the probability that the part of the technological era they were born in was the first 100 years. This is easier to work out, it's 100/L_years(technological_era) but, unfortunately that's also the probability they are born in the second 100 years of a technological era of the same length, the third 100, the last 100 etc. so I don't think it gives us any predictive power?
That just leads you down the road of discarding probabilities. Since something either happens or doesn't happen, the probability is either 100% for the things that will happen or 0% for those that do not. This is not a helpful position to take, although it is technically correct, in some not very useful sense.
Humans are good at dealing in counterfactuals. 'What would have happened if I hadn't missed the bus?' is a useful question to ask, even if you did miss the bus. What would I be like if I hadn't gone to university/had taken that job/never killed my parents? Obviously the 'I' in those questions cannot be you, exactly, since you did or didn't do those things. But it's still a useful concept or thought experiment, and can give us valuable insights.
The commenter is using 'I' in that counterfactual sense. And certainly, I understood what they meant by it, so they were successful in communicating (at least, to me) which is what matters with language.
>it's extremely unlikely to be born at the first 100 years (0.00005 %).
similar example - throw a coin 21 time and record result. Now look at that recorded result and behold how unlikely that result is, like one in 2^21 (0.00005%), yet you got it despite the odds :)
Yeah of course, but... all results are equally likely, but some are "interesting" or "meaningful", like all tails or all heads. If it's 21 tails, it's pretty much certain that something is not right, that it's not a fair coin.
In a Bayesian point of view, let's pick some prior probability distribution over lengths of human survival and consider the current age of humanity as a random variable. This gives the posterior probability over lengths of human survival.
I'm having trouble writing out a detailed refutation, but it seems highly speculative to deduce much solely from the notion that "it is very unlikely one would be born in in the first few years of a long technological age".
I do think that analyzing the stability and trajectory of civilization is very interesting.
> The UU Professor of Anthropics had developed the Special and Inevitable Anthropic Principle, which was that the entire reason for the existence of the universe was the eventual evolution of the UU Professor of Anthropics.
> But this was only a fomal statement of the theory which absolutely everyone, with only some minor details of a `Fill in name here’ nature, secretly believes to be true.
> The Participatory Anthropic Principle states not only that the Universe had to develop humanity (or some other intelligent, information-gathering life form) but that we are necessary to it’s existence, as it takes an intelligent observer to collapse the Universe’s waves and probabilities from superposition into relatively concrete reality.
This is a misunderstanding of what quantum waveform collapse is. It requires an "observation", but not an intelligent observer. For example, in the Schrodinger's Cat thought experiment, the Geiger Counter is a perfectly valid observer.
I think you hit on the critical point where this theory goes awry, which is the idea that there is something special about human or animal intelligence which puts it in an entirely different category of other types of information gathering and synthesis. Another option is that the way people gather and synthesize information is just an advanced form of the same processes common to other dynamic systems, localized in layers of biology to create extreme forms of self-referential analysis. It's been a long debate, but the development of artificial intelligence is likely to significantly change the dominant perspective. If we continue to create ever more complex systems that behave intelligently but don't have the same kind of self-awareness as people perceive, we might be able to untangle the concepts of perception, intelligence, creativity, and the sense of self.
What's the criteria for what counts as an observer? Geiger counters are, but some photon detectors in a delayed choice quantum eraser experiment[1] aren't?
Basically there is no sharp division, but the more the observation spreads, the harder it is to reverse. For one isolated particle, it's easiest. Anything we can reliably read is basically permanent, like a bit flip in a computer.
So once a photon is detected, like by making a mark on a screen or camera, it's permanent. In the delayed-choice experiment this happens twice, once for the "interference pattern" and again after the choice.
If you accept that, which I think is intuitive, then it makes the DCQE much easier to grasp. If you want to understand the experiment better, I would recommend this thread:
I think you're misunderstanding the Schrodinger's cat paradox. First, the paradox is that the cat is both alive and dead until you open the box to observe it. Second, the whole point of the paradox is to show how absurd waveform collapse is.
To state the Weak Anthropic Principle in a form that feels (at least to me) less like philosophical woo: "Universes that cannot be inhabited by intelligent observers are never observed, because there cannot be anyone there to do the observing".
Right. But the way it was stated in the article makes it easy to think of it as the universe requiring rather than the observer requiring. The other versions explicitly get into that kind of nonsense; I wanted to state the weak version in a way that made it clear that it didn't go there.
(I suspect that this page states the weak version in that way in order to make the other versions seem more similar.)
An /observed/ universe requires conditions to cause observers to evolve.
I don't but that an "intelligent" observer is needed to collapse the waveform, BTW. That uses a very non-physical interpretation of "observer." Any particle that can absorb information, can be said to be "observing." As simple as a reaction that depends on temperature would do it.
The Final Anthropic Principle follows naturally from the Weak/Strong Anthropic Principle. Once intelligence has evolved and observed the Universe with a single first thought, why didn't it then die out? Of course the definition of Intelligence is arguable, anything from a vaguely self-aware rodent to a literature-reading human, and beyond. If we take some person called Ubuntu who discovered how to control fire 130,000 years ago at age 23 years and 7 months in southern Mozambique as having the very first aware thought, then straight afterwards there'd be no more anthropic principle at work causing intelligence to exist in the Universe. The fact we're still here, our small tribe of sole humans not eaten by hyenas or our planet not extinguished by nukes, suggests there could be a Final Anthropic Principle at work.
"Once intelligence has evolved and observed the Universe with a single first thought, why didn't it then die out?"
What proof, line of reasoning, logical principle, or evidence do you have to believe that a single first thought would lead to anything dying out? What makes you think there is some underlying Anthropic Principle at work in the universe?
Saying something could be at work is more or less saying "God did it". It doesn't explain or illuminate anything.
It only takes a single first thought by an intelligence to observe the Universe. Everything occurring up to then (e.g. nucleii, carbon, brains) is highly unlikely and therefore many people suggest an Anthropic Principle to explain it.
Once that single first thought by an intelligence has occurred, the Weak or Strong Anthropic Principle is no longer required to explain the existence of intelligence, and so its continuance has the same unlikeliness as other life forms, i.e. ultimate extinction. The fact humans became the opposite of extinct (e.g. fire, scrolls, nukes) suggests that if the Anthropic Principle applies to the emergence of intelligence, something even "stronger" such as the Final Anthropic Principle could apply to the continuance of intelligence.
I'm not saying there's an underlying Anthropic Principle in the Universe. I'm answering the question to show that the Final Anthropic Principle is as scientific a proposal as anything else.
That's not a scientific proposal. There is absolutely no reason to think that anything should cease existing simply because the first thought occurred.
And here's a quote from it: "it would be possible for each male to be matched not merely with the most beautiful woman in the world . . . but to be matched with the most beautiful woman whose existence is logically possible."
Why are planetary orbits roughly circular? Is it because
(a) if they were any other shape (e.g. very long isosceles triangles) conditions wouldn't be suitable for intelligent life to evolve, and we wouldn't be around to observe it, or
(b) Newton's law of gravity constrains them to conic sections. Stable orbit of single planets must be circular or elliptical. Any planets with highly eccentric orbits would have been ejected from the early solar system, leaving only those which are roughly circular?
Of course, the answer is (b), i.e. instead of the emergence of intelligent life determining the laws of physics, the laws of physics allow the evolution of intelligent life. But we only agree on that because we already know Newton's law of gravity. If we didn't know it, some people would believe (a) while others would think that one day a law of gravity would be found which determines planetary motion.
I don't have the causality backwards. We don't have a complete knowledge of the laws of physics, and we have something which is unexplained. Whenever this was the case in the past, better laws were found which closed the explanatory gap. Why should it be any different this time?
The point of the anthropic principle isn't to explain it, it's to point out that an explanation is not required.
We could find that the laws of our universe are the only possible set of physical laws. This would be the expectation of the Newtonian era. In that case there is nothing to explain. Or it may be, and currently seems likely, that there are many possible sets of physical laws. Then the question of why we happen to have one of the perhaps very few possible sets of physical laws that allows intelligent life to develop seems to require an explanation. The anthropic principle explains why it really doesn't, because in the (possible or actual) universes where intelligent life is impossible, the question simply doesn't come up.
The point of the anthropic principle is precisely that we shouldn't expect to close the explanatory gap, because there isn't one. We shouldn't be surprised if physical laws seem to be "tuned" to allow intelligent life to emerge.
Imagine that planets orbited in randomly selected geometric shapes, and we happened to be on the only known elliptical one, giving us the conditions required for life. Would this lucky fact require explanation?
>Imagine that planets orbited in randomly selected geometric shapes, and we happened to be on the only known elliptical one, giving us the conditions required for life. Would this lucky fact require explanation?
No more than the existence of a planet of the right size at the right distance from the sun. You still have physical laws which determine what's possible, but they probably won't (and, in fact, don't) provide a complete explanation.
The weakest form of the Anthropic Principle is uncontroversial. For example, we can use it to conclude that physical laws which don't permit intelligent life to evolve must be wrong. Can we use it to rule out physical laws which don't entail the evolution of intelligent life? I would argue yes, but that doesn't require any fine-tuning of dimensionless constants: an infinite (e.g. Einstein-de Sitter) universe, or Everett's Many Worlds interpretation of quantum mechanics would entail it, given its possibility.
